In a wireless communication system, a base station provides one or more coverage areas, such as cells or sectors, in which the base station can serve wireless communication devices (WCDs), such as cell phones, wirelessly-equipped personal computers or tablets, tracking devices, embedded wireless communication modules, or other devices equipped with wireless communication functionality.
In general, each coverage area could operate on one or more carriers each defining one or more ranges of frequency spectrum and having a respective downlink channel for carrying communications from the base station to UEs and a respective uplink channel for carrying communications from the UEs to the base station. Such carriers could be frequency division duplex (FDD), in which the downlink and uplink channels are defined as separate respective ranges of frequency, or time division duplex (TDD), in which the downlink and uplink channels are defined on a common range of frequency but are distinguished through time division multiplexing. Further, the downlink channel and uplink channel of each carrier could also be divided into respective sub-channels for carrying particular communications, such as one or more control channels for carrying control signaling and one or more traffic channels for carrying application-layer data and other traffic.
In an example system, for instance, the air interface could be divided over time into frames and sub-frames each defining two slots, and the uplink and downlink channels could each be divided over their frequency bandwidth into sub-carriers that are grouped within each slot into resource blocks, with portions of each sub-frame further defining various control channels for signaling communication between the base station and WCDs.